The present invention relates to the manufacture and restoration of metal components, such as components of gas turbine engines. In particular, the present invention relates to diffusion bonding techniques for manufacturing and repairing metal components.
Superalloys of nickel and cobalt are typically employed in gas turbine engine components due to the high mechanical strengths and creep resistances obtained with such materials. Because gas turbine engine components are exposed to extreme temperatures and pressures, high mechanical strengths and creep resistances are required to preserve the integrity of the engine over the course of operation. However, over time, exposed portions of the components are subject to wear and other degradations, which can lead to reductions in operational efficiencies.
Due to economic factors, it is common practice in the aerospace industry to restore turbine engine components rather than replace them. Such restorations desirably restore damaged regions of the engine components to their original dimensions. One area of practice that has been a major interest to the aerospace industry for restoring turbine engine components involves the joining of the superalloy parts. Current joining techniques such as laser welding processes and tungsten inert gas welding processes are suitable for joining superalloy components. However, these techniques may induce crack formations in the metal components, which can also reduce operational efficiencies.
Other joining methods, such as brazing techniques, can be time consuming due to post-bond heat treatments. For example, brazing operations typically subject the superalloys of the engine components to high temperatures for extended durations. Exposure to the high temperatures for the extended durations may reduce the low-temperature creep resistances of the superalloys, particularly with single crystal alloys. Additionally, the brazed engine components typically have polycrystalline microstructures, which have lower mechanical strengths and creep resistances compared to the microstructures of single crystal alloys. Accordingly, there is a need for improvements to the existing joining techniques to meet the more demanding requirements when joining high performance materials.